eat a whole bunch of tootsie rolls and save the wrappers, then set them all up in a cool little design where they're all touching eachother....set the first one on fire....
they burn nice and slow, so it's a nice way to spend time depending on how many you have my mom quickly threw away any wrappers she seen around cuz she knew what i was plannin
If you cut the handles off about 50 sparklers and wrap them in several layers of packing tape so no gas can escape (leaveing one sticking halfway out as a fuse) you can get a very nice exploseive with a little shrapnel (have everything you like atleast 100 feet from it when it goes off). Also If you turn on your stove and mix potasuim nitrate (salt peter from the pharmacy or as fertiliser from a feed store) 60:40 with sugar untill its melted and light that on fire it makes a great ploom of smoke I filled a parkinglot with smoke once. Finally if you mix aluminium power with Powdered Iron Oxide and light it up with a sparkler it gets really hot, it can mealt right through the engine block of a car if you have enought of it.